package backtype.storm.transactional.partitioned;

import java.util.Map;

import backtype.storm.coordination.BatchOutputCollector;
import backtype.storm.task.TopologyContext;
import backtype.storm.topology.IComponent;
import backtype.storm.transactional.TransactionAttempt;


/**
 * This interface defines a transactional spout that reads its tuples from a
 * partitioned set of brokers. It automates the storing of metadata for each
 * partition to ensure that the same batch is always emitted for the same
 * transaction id. The partition metadata is stored in Zookeeper.
 */
public interface IPartitionedTransactionalSpout<T> extends IComponent {
    public interface Coordinator {
        /**
         * Return the number of partitions currently in the source of data. The
         * idea is is that if a new partition is added and a prior transaction
         * is replayed, it doesn't emit tuples for the new partition because it
         * knows how many partitions were in that transaction.
         */
        int numPartitions();


        /**
         * Returns true if its ok to emit start a new transaction, false
         * otherwise (will skip this transaction).
         * 
         * You should sleep here if you want a delay between asking for the next
         * transaction (this will be called repeatedly in a loop).
         */
        boolean isReady();


        void close();
    }

    public interface Emitter<X> {
        /**
         * Emit a batch of tuples for a partition/transaction that's never been
         * emitted before. Return the metadata that can be used to reconstruct
         * this partition/batch in the future.
         */
        X emitPartitionBatchNew(TransactionAttempt tx, BatchOutputCollector collector, int partition,
                X lastPartitionMeta);


        /**
         * Emit a batch of tuples for a partition/transaction that has been
         * emitted before, using the metadata created when it was first emitted.
         */
        void emitPartitionBatch(TransactionAttempt tx, BatchOutputCollector collector, int partition,
                X partitionMeta);


        void close();
    }


    Coordinator getCoordinator(Map conf, TopologyContext context);


    Emitter<T> getEmitter(Map conf, TopologyContext context);
}
